Covalent
organic frameworks (COFs) are a relatively new class of
organic nanostructured porous materials, formed by covalent bonds
between light elements, with high surface area. The thermal conductivity
values (k) for some COFs (COF-300, RIO-1, RIO-4,
RIO-20) were measured using the modified transient plane source (MTPS)
technique. Values ranging from 0.038 to 0.048 W m–1 K–1 were measured depending on the COF pore structure
and surface area. Thermal conductivities correlate linearly with the
inverse of the cross-sectional area of the pores.
A thermally stable carbocationic covalent organic network (CON), named RIO‐70 was prepared from pararosaniline hydrochloride, an inexpensive dye, and triformylphloroglucinol in solvothermal conditions. This nanoporous organic material has shown a specific surface area of 990 m2 g−1 and pore size of 10.3 Å. The material has CO2 uptake of 2.14 mmol g−1 (0.5 bar), 2.7 mmol g−1 (1 bar), and 6.8 mmol g−1 (20 bar), the latter corresponding to 3 CO2 molecules adsorbed per pore per sheet. It is shown to be a semiconductor, with electrical conductivity (σ) of 3.17×10−7 S cm−1, which increases to 5.26×10−4 S cm−1 upon exposure to I2 vapor. DFT calculations using periodic conditions support the findings.
This contribution presents four dye-based CONs derived from the reaction of triformylphloroglucinol with thionin acetate (RIO-43), safranin chloride (RIO-51), phenosafranin (RIO-47), and Bismarck brown Y (RIO-55). These materials, called Covalent Organic Networks (CONs), are insoluble solids formed by organic lamellar stacked structures and present permanent porosity, light absorption across the whole visible spectrum, fluorescence, ion exchange capability, and ion and electron conductivity. Periodic DFT calculations carried out indicated that the bent nature of most of those building blocks affords conductive extended materials containing pores with the shape of three-petal flowers, with the anion positioned at the petals. The turbostratic disorder makes only the center of the flower-shaped pores accessible, decreasing the specific surface areas. The material that has a higher surface area is the one derived from thionin acetate (RIO-43), such as the highest electrical conductivity (1.96 × 10 -5 S cm −1 ), followed by RIO-47 (1.12 × 10 -7 S cm −1 ), RIO-55 (1.58 × 10 -7 S cm −1 ) and RIO-51 (3.26 × 10 -7 S cm −1 ).
Five Covalent Organic Frameworks (COFs) were synthesized and applied to Dye-Sensitized Solar Cells (DSSCs) as dyes and additives. These porous nanomaterials are based on cheap, abundant commercially available ionic dyes (thionin acetate RIO-43, Bismarck brown Y RIO-55 and pararosaniline hydrochloride RIO-70), and antibiotics (dapsone RIO-60) are used as building blocks. The reticular innovative organic framework RIO-60 is the most promising dye for DSSCs. It possesses a short-circuit current density (Jsc) of 1.00 mA/cm2, an open-circuit voltage (Voc) of 329 mV, a fill factor (FF) of 0.59, and a cell efficiency (η) of 0.19%. These values are higher than those previously reported for COFs in similar devices. This first approach using the RIO family provides a good perspective on its application in DSSCs as a dye or photoanode dye enhancer, helping to increase the cell’s lifespan.
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